Conventional methods to interconnect Fiber-Optic (FO) cables for well applications involve splicing or use of FO-connectors.
In a splice, adjacent ends of fiber are aligned and fused together. A good splice does not show significant signal loss, typically <0.01 dB, or distortion. However, splicing is difficult to deploy and is therefore not available for use in oilfield applications.
In a FO connector, the fiber is glued in a ceramic ferrule. The intermeshing connector sections then align and center these ferrules, i.e. the ends of the fibers, against each other. Such connections show some signal loss and distortion. In a good FO-connection this loss is of the order of 0.1 dB.
It is known to in-situ interconnect optical fibers in a well by wet-connectable FO connectors, which have to center and align the cores of the interconnected optical fibers, which cores may have a diameter of only 10 micrometer.
The problem of interconnecting optical fibers downhole or at wellhead assemblies has until now been solved by mating intermeshing connector assemblies with extreme (micrometer) precision at similarly extreme costs.
Installation of fiber optical sensing and/or communication systems in oil and/or gas production wells may generate leakage paths since the fiber optical cables and/or connectors will penetrate pressure barriers, such as downhole packers, the cement sheath surrounding the well casing, the tubing hanger near the wellhead and the wellhead assembly itself.
Another problem associated with installation of optical sensing and/or communication systems in oil and/or gas production wells in which the downhole pressure may be several hundred Bar, is that optical fibers cannot sustain significant shear forces. Therefore conventional fiber optic penetrators for pressure barriers are multicomponent and comprise several materials, including degradation prone elastomers. The long-term mechanical behavior of such a multicomponent system is doubtful.
U.S. Pat. No. 4,994,671 discloses a production logging tool for analyzing the composition of formation fluids in a downhole test chamber in which a light source emits near infrared rays via collimation or fiber optics. The collimation means may comprise a collimating mirror, a first fiber optic bundle for directing the near infrared rays to a substantially transparent window of the test chamber and a second fiber optic bundle for directing light reflected by the formation fluid to a spectrometer for detecting the composition of the formation fluid.
In the known production logging tool the first and second fiber optic bundles are arranged in the test chamber at the same side of the light transparent window.
There is a need for an improved and cost efficient system and method for interconnecting fiber optical cables in wells or other hydrocarbon fluid production facilities, which permits interconnection of fiber optical cables that are arranged at opposite sides of a pressure resistant light transparent window.